Pressure process for condensing power house steam

ABSTRACT

A method of operating a steam turbine system comprising, leading the steam from the turbine to a pump automatically regulated to maintain a low pressure for preventing turbine back-pressure at all turbine loads, leading the steam from the pump to a heatexchanger and condenser wherein it is allowed to build up pressure to a desired level, setting that level externally and automatically maintaining that level internally within reasonable limits by varying the surface area of heat exchange being used.

[22] Filed:

United States Patent Cassidy [54] PRESSURE PROCESS FOR CONDENSING POWER HOUSE STEAM [72] Inventor: James L. Cwsidy, 66 Prospect Street, Turners Falls, Mass. 01376 Dec. 3, 1970 [21] App]. N0.: 94,881

521 U.S.Cl. ..60/95 51 Int.Cl ..F01n 7/00 58 FieldofSearch ..60/36,38,95,96, 10s

[56] References Cited- UNITED STATES PATENTS 3,257,806 6/1966 Stahl; ..60/38 X NOV. 28, 1972 FOREIGN PATENTS OR APPLICATIONS 262,837 12/1926 Great Britain .....60/36 Primary Exanuner-Martin P. Schwadron Assistant Examiner-A. M. Ostrager AttomeyRoss & Flavin ABSTRACT A method of operating a steam turbine system comprising, leading the steam from the turbine to a pump automatically regulated to maintain a low pressure for preventing turbine back-pressure at all turbine loads, leading the steam from the pump to a heat-exchanger and condenser wherein it is allowed to build up pressure to a desired level, setting that level externally and automatically maintaining that level internally within reasonable limits by varying the surface area of heat 1 exchange being used.

4 China, 2 Drawing Figures PATENTEDmvze I972 FIG.|.

BTU/ LB.

FIG.2.

3000 LBS/S0. INJABS. 695 FA H M.

PRESSURE PROCESS FOR CONDENSING POWER HOUSE STEAM Exhaust power house steam in present practice is caused to lose its latent heat energy in a vacuum condensing chamber before being returned to the boilers as condensate. This is an isothermal condensation as the temperature of the condensate is essentially the same as that of the exhaust steam. When the steam passed through the turbine it underwent adiabatic expansion, that is, all heat energy was transfered to mechanical energy and, within reasonable limits, none was lost. It would, on the face of it, seem futile to reverse the process and return the exhauststeam to the boiler by adiabatic compression. But actually there are compensating advantages to be gained by returning the exhaust steam by a combination of adiabatic and isothermal compressions.

It is a thermodynamic fact that the amount of latent heat energy per poundof saturated steam decreases with increase in pressure and so does its entropy which is its latent heat per degree Kelvin. Thus, condensation under higher pressure is equivalent to using a drive medium of lower entropy.

At higher pressures and therefore temperatures the coolant effluent can be rendered as heated vapor, air, or secondary steam, thus making it unnecessary to return heated coolant water to rivers as hydro-thermal pollutant, a major aim of this invention.

Factors further contributing to the usefulness and economy of this process are that the secondary steam may be used or sold and its condensate being a distillate may also be used as such or can be used over and over as coolant where water is scarce such as in ecologically prefered locations for atomic-steam plants.

This invention, then, is a process or system for partially repressurizing and condensing exhaust steam while it is being held at a desired pressure and loses latent heat energy commensurate to its pressure, the coolant effluent being heated vapor, air, or secondary steam. An arrangement of, existing equipment is specified as part of the process or system to accomplish the handling of a varying volume of input steam at a reasonably constant pressure for stabilizing entropy considerations.

BACKGROUND In a modern steam power plant exhaust steam from turbines is cooled and condensed in a vacuum type condenser or heat-exchanger in a large chamber just beneath the turbine. It is cooled by pipes circulating river water, the heated effluent of which when returned to the steam constitutes hydro-thermal pollutant. Measures have been taken in the form of huge expensive cooling towers to cool the hot effluent below legally imposed limits before returning it to the stream.

THE PROCESS In the application of the new process to an existing plant it is only necessary to tap into the present conthe coolant flow to the chamber and the condensate exit, then open a valve to the repressun'zing pump. This starts the process. This pump or pumps should have a capacity capable of handling the entire volume of exhaust at highest turbine output. It is to be driven by a motor, engine, or other means whose speed is to be automatically regulated to pace turbine output thus keeping the chamber pressure low, as near as possible to present practice.

The pump delivers the steam to a forced air and/or spray cooled or immersion heat exchanger the internal pressure of which is maintained at a desired level. The condensate, still under pressure is delivered to a conventional boiler injection pump.

In order to maintain a desired pressure in the heat exchanger while the steam loses latent heat and contracts and the incoming volume varies with turbine load, the exchanger is built in sections so arranged that a larger exchanger surface is presented for a greater volume of steam. This is accomplished by having the sections closed off one from the other by valves which, controlled by internal pressure, operate in cascade or series fashion. The first section should be capable of taking care of a minimal volume of steam controling minor fluctuations of pressure with the forced air and temal pressure and also the air and spray volume which stabilize the pressure again. 7 If incoming volume of steam continues to increase and pressure with it, the process is repeated, another section is opened and so on to full capacity. The opening and closing pressures is less for each succeeding valve thus when incoming volume lessens and pressure falls, the last section to open will be the first to close which keeps the ratioof heat exchange surface to volume of incoming steam reasonably constant so that internal pressure likewise remains reasonably constant.

The automatic internal pressure sensors that control the valves may be adjusted or set from outside so as to maintain any desired pressure to suit whatever conditions that pertain. The housing of the sections may be fairly open if it is desired to release heated vapor directly into the atmosphere, or closed in when secon dary steam is desired in which case the forced air would be omitted.

in special cases such as when an atomic plant is to be densed and used over and over.

DESCRIPTION OF DRAWING The accompanying drawing is essentially a flow chart of the new process or system. In FIG. 1 the numeral 1 designates a condensing chamber beneath a turbine in a conventional steam power plant. Before starting the process valves 15 and 18 are to be closed thereby shutting down'the vacuum process and eliminating densing chamber with a suitable steam duct, shutoff hydro-thennal pollution of the river by cutting off the flow of heated coolant efiluent from valve 17. Simultaneously valve 16 is opened and the exhaust steam is taken up by pump or pumps 2 which is driven by motor or engine 3, regulated as to speed by pressure sensor 6. From the pump the steam is delivered to heat exchanger 4 where it is retained in the first section thereof by valves 13 and 20 until a desired pressure is built Meanwhile meanwhile the steam is losing latent heat to the coolant spray being circulated by pump 11 and abetted by forced air fan 19 both these being controled by sensor 12. After losingan amount of latent heat commensurate with its pressure the steam condenses and the condensate still under pressure passes through valve 20 to the conventional boiler injection pump, not shown. I A

Since it is desirable to hold the exhaust steam at a definite pressure while it loses latent heat and shrinks in volume as it condenses meanwhile being augmented by a varying volume of incoming steam, the heat exchanger is built in sections separated one from another by automatic valves opened and closed by pressure sensors the purpose of which is to keep the area of heat exchange surface reasonably proportionate to internal pressure. The exchanger should be designed so that one section will suffice to handle the minimal volume of steam experienced in practice, minor variations of which will be taken care of by variations in theforced air and spray delivery controled by sensor 12. With increase in the volume of incoming steam the internal pressure will increase and at a predetermined limit valve 13 will open adding an additional section. This will cause a temporary drop in pressure which is to be compensated for by lessened spray and air delivery. If incoming steam volume continues to increase another section is opened as by valve 15 and so on to full capacity. Each succeeding valve is to be set to open and close at a slightly lower pressure than the preceding one in this way when incoming steam volume lessens, the last section to open will be the first to close thus reversing the sequence.

Pump, or pumps, 2 is to have the capacity to handle the full volume of exhaust steam delivered by the turbine at full load so as to keep the pressure in the exhaust chamber low, as near to the present operating gradient as possible.

At the higher temperatures of heat exchange in the new process the coolant effluent will be heated vapor, air, or secondary steam. If so desired the exchanger may be located on the roof and the vapors dissipated directly into the atmosphere. Where secondary steam is desired the exchanger housing is to be enclosed, the intemal pressure limits properly set and the secondary steam led ofi by a duct such as 10.

FIG. 2 shows graphically the relationship between the latent heat content and the pressure and temperature of saturated steam. Since entropy is expressed by the latent heat per degree Kelvin, it too will decrease at higher pressures. The graph is merely illustrative of the fact that saturated steam has a lower latent heat content and entropy at higher pressures, the figures will be found in any thermodynamic text book treating of saturated steam.

What is claimed is:

l. A method of operating a steam turbine system comprising, leading the steam from the turbine to a pump automatically regulated to maintain a low pressure for preventing turbine back-pressure at all turbine loads, leading the steam from the pump to. a heatexchanger and condenser wherein it is allowed to build up pressure to a desired level setting that level exter nally and automatically maintaining that level internally within reasonable limits by varying the surface area of heat exchange being used.

2. A method of operating a steam turbine system according to claim 1, wherein the surface area of heat exchange is varied and controlled by sensors in a sectionalized body so constructed that additional sections are automatically opened in series fashion in direct relation to the volume of impressed steam as it increases and simultaneously in inverse relation to the rate of condensation as it decreases, and automatically closed in reverse order with decrease in steam input and/or increase in rate of condensation.

3. A method of operating a steam turbine system according to claim 1, including circulating a coolant and its heated effiuent in the heat-exchanger condenser and disposing of the heated effluent as steam or as expendable heated vapor, gas or air at a pressure sufficiently high to make it commercially usable.

4. A method of operating a steam turbine system according to claim 1, wherein the condensate is returned from the heat-exchanger condenser to the turbine boilers. 

1. A method of operating a steam turbine system comprising, leading the steam from the turbine to a pump automatically regulated to maintain a low pressure for preventing turbine backpressure at all turbine loads, leading the steam from the pump to a heat-exchanger and condenser wherein it is allowed to build up pressure to a desired level setting that level externally and automatically maintaining that level internally within reasonable limits by varying the surface area of heat exchange being used.
 2. A method of operating a steam turbine system according to claim 1, wherein the surface area of heat exchange is varied and controlled by sensors in a sectionalized body so constructed that additional sections are automatically opened in series fashion in direct relation to the volume of impressed steam as it increases and simultaneously in inverse relation to the rate of condensation as it decreases, and automatically closed in reverse order with decrease in steam input and/or increase in rate of condensation.
 3. A method of operating a steam turbine system according to claim 1, including circulating a coolant and its heated effluent in the heat-exchanger condenser and disposing of the heated effluent as steam or as expendable heated vapor, gas or air at a pressure sufficiently high to make it commercially usable.
 4. A method of operating a steam turbine system according to claim 1, wherein the condensate is returned from the heat-exchanger condenser to the turbine boilers. 